staging: iio: isl29028: correct proximity sleep times

The sysfs attribute in_proximity_sampling_frequency_available currently
shows the values 1 3 5 10 13 20 83 100. These values are supposed to
correspond to the sleep values 800 400 200 100 75 50 12.5 0 (all in ms).
When passing in a sampling frequency of 3, it actually uses a sleep
time of 200ms instead of the expected 400ms value. This patch changes
the value shown by this sysfs attribute to use fixed-point numbers so
that the correct sampling frequency is shown to the user. This patch
also changes the code that updates the proximity sampling frequency to
only allow values that are shown in the _available sysfs attribute.

The original code showed the value 83 that corresponds to the sleep
time 12 ms. The data sheet actually lists 12.5 ms as the sleep time,
so the proximity frequency was updated to 80.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/light/isl29028.c

@@ -64,8 +64,25 @@
 
 #define ISL29028_POWER_OFF_DELAY_MS		2000
 
-static const unsigned int isl29028_prox_sleep_time[] = {800, 400, 200, 100, 75,
-							50, 12, 0};
+struct isl29028_prox_data {
+	int sampling_int;
+	int sampling_fract;
+	int sleep_time;
+};
+
+static const struct isl29028_prox_data isl29028_prox_data[] = {
+	{   1, 250000, 800 },
+	{   2, 500000, 400 },
+	{   5,      0, 200 },
+	{  10,      0, 100 },
+	{  13, 300000,  75 },
+	{  20,      0,  50 },
+	{  80,      0,  13 }, /*
+			       * Note: Data sheet lists 12.5 ms sleep time.
+			       * Round up a half millisecond for msleep().
+			       */
+	{ 100,  0,   0 }
+};
 
 enum isl29028_als_ir_mode {
 	ISL29028_MODE_NONE = 0,
@@ -76,32 +93,37 @@ enum isl29028_als_ir_mode {
 struct isl29028_chip {
 	struct mutex			lock;
 	struct regmap			*regmap;
-	unsigned int			prox_sampling;
+	int				prox_sampling_int;
+	int				prox_sampling_frac;
 	bool				enable_prox;
 	int				lux_scale;
 	enum isl29028_als_ir_mode	als_ir_mode;
 };
 
-static int isl29028_find_prox_sleep_time_index(int sampling)
+static int isl29028_find_prox_sleep_index(int sampling_int, int sampling_fract)
 {
-	unsigned int period = DIV_ROUND_UP(1000, sampling);
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(isl29028_prox_sleep_time); ++i) {
-		if (period >= isl29028_prox_sleep_time[i])
-			break;
+	for (i = 0; i < ARRAY_SIZE(isl29028_prox_data); ++i) {
+		if (isl29028_prox_data[i].sampling_int == sampling_int &&
+		    isl29028_prox_data[i].sampling_fract == sampling_fract)
+			return i;
 	}
 
-	return i;
+	return -EINVAL;
 }
 
 static int isl29028_set_proxim_sampling(struct isl29028_chip *chip,
-					unsigned int sampling)
+					int sampling_int, int sampling_fract)
 {
 	struct device *dev = regmap_get_device(chip->regmap);
 	int sleep_index, ret;
 
-	sleep_index = isl29028_find_prox_sleep_time_index(sampling);
+	sleep_index = isl29028_find_prox_sleep_index(sampling_int,
+						     sampling_fract);
+	if (sleep_index < 0)
+		return sleep_index;
+
 	ret = regmap_update_bits(chip->regmap, ISL29028_REG_CONFIGURE,
 				 ISL29028_CONF_PROX_SLP_MASK,
 				 sleep_index << ISL29028_CONF_PROX_SLP_SH);
@@ -112,16 +134,18 @@ static int isl29028_set_proxim_sampling(struct isl29028_chip *chip,
 		return ret;
 	}
 
-	chip->prox_sampling = sampling;
+	chip->prox_sampling_int = sampling_int;
+	chip->prox_sampling_frac = sampling_fract;
 
 	return ret;
 }
 
 static int isl29028_enable_proximity(struct isl29028_chip *chip)
 {
-	int sleep_index, ret;
+	int prox_index, ret;
 
-	ret = isl29028_set_proxim_sampling(chip, chip->prox_sampling);
+	ret = isl29028_set_proxim_sampling(chip, chip->prox_sampling_int,
+					   chip->prox_sampling_frac);
 	if (ret < 0)
 		return ret;
 
@@ -132,8 +156,12 @@ static int isl29028_enable_proximity(struct isl29028_chip *chip)
 		return ret;
 
 	/* Wait for conversion to be complete for first sample */
-	sleep_index = isl29028_find_prox_sleep_time_index(chip->prox_sampling);
-	msleep(isl29028_prox_sleep_time[sleep_index]);
+	prox_index = isl29028_find_prox_sleep_index(chip->prox_sampling_int,
+						    chip->prox_sampling_frac);
+	if (prox_index < 0)
+		return prox_index;
+
+	msleep(isl29028_prox_data[prox_index].sleep_time);
 
 	return 0;
 }
@@ -361,7 +389,7 @@ static int isl29028_write_raw(struct iio_dev *indio_dev,
 			break;
 		}
 
-		ret = isl29028_set_proxim_sampling(chip, val);
+		ret = isl29028_set_proxim_sampling(chip, val, val2);
 		break;
 	case IIO_LIGHT:
 		if (mask != IIO_CHAN_INFO_SCALE) {
@@ -439,7 +467,8 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 		if (chan->type != IIO_PROXIMITY)
 			break;
 
-		*val = chip->prox_sampling;
+		*val = chip->prox_sampling_int;
+		*val2 = chip->prox_sampling_frac;
 		ret = IIO_VAL_INT;
 		break;
 	case IIO_CHAN_INFO_SCALE:
@@ -472,7 +501,7 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 }
 
 static IIO_CONST_ATTR(in_proximity_sampling_frequency_available,
-				"1 3 5 10 13 20 83 100");
+				"1.25 2.5 5 10 13.3 20 80 100");
 static IIO_CONST_ATTR(in_illuminance_scale_available, "125 2000");
 
 #define ISL29028_CONST_ATTR(name) (&iio_const_attr_##name.dev_attr.attr)
@@ -571,7 +600,8 @@ static int isl29028_probe(struct i2c_client *client,
 	}
 
 	chip->enable_prox  = false;
-	chip->prox_sampling = 20;
+	chip->prox_sampling_int = 20;
+	chip->prox_sampling_frac = 0;
 	chip->lux_scale = 2000;
 
 	ret = regmap_write(chip->regmap, ISL29028_REG_TEST1_MODE, 0x0);